The present invention relates to the art of hydraulic mechanisms and, more particularly, to a gear type hydraulic mechanism having variable speed and variable torque capabilities.
The present invention finds particular utility as a hydraulic motor and accordingly will be disclosed and described in detail in connection with such use. At the same time, however, it will be appreciated that the invention is applicable to mechanisms other than motors, such as hydraulic pumps and transmission mechanisms for example.
A wide variety of gear type hydraulic motors and pumps have been provided heretofore having variable speed, volume and/or torque capabilities, which capabilities are generally achieved by changing the relative positions of component parts of the mechanism. Efforts have also been made heretofore to provide gear type hydraulic transmissions having variable speed and torque capabilities through the use of a plurality of gear type motors or pumps. In connection with such latter efforts, a plurality of gear type hydraulic motors are longitudinally arranged with respect to the axis of an output shaft and are adapted to be sequentially actuated in response to hydraulic fluid supplied under varying pressure to a hydraulic flow control system for the motors.
Variable hydraulic mechanisms of the foregoing character are structurally complex and expensive with respect to both the construction thereof and to the arrangements by which variable operation is achieved. Generally, such prior mechanisms are not very efficient in operation and are undesirably limited with respect to the magnitude of the variable characteristics which can be realized and/or their versatility with respect to use. The foregoing disadvantages in such prior mechanisms are due in part and in certain instances to the number and/or mass of the gears to be hydraulically driven, and from relative dispositions of the gears which result in the undesirable application or distribution of forces on the component parts during use and operation.